摘要
纵扭复合超声振动辅助铣削(LTUVAM)是在刀具轴向与扭转方向上施加高频微幅振动的一种辅助铣削技术,具有降低切削力与切削热、提高工件表面质量、提高表面残余压应力、减少刀具磨损等诸多优点。本文围绕难加工材料的铣削加工进行了系统综述。在设备制造方面,阐述了纵扭复合超声振动系统的结构设计方法与工作原理;在工艺开发方面,从LTUVAM的切削刃运动轨迹及切削特性入手,分析各类材料的切削加工性能,并总结了LTUVAM的优势及应用。最后,本文对LTUVAM的未来发展趋势进行展望。
随着现代制造业对材料及零部件性能要求的不断提高,许多均质合金材料(如铝合金、钛合金)和复合材料(如硅铝合金、铝基碳化硅、碳纤维增强复合材料)等难加工材料,因具有高硬度、高强度、高耐磨性、耐腐蚀性和抗疲劳性而被大量投入应用。然而,其拥有优异物理力学性能的同时也具有难切削加工性,传统加工中极易出现表面质量差、加工精度低、刀具磨损严重等问题。同时,许多比强度高、结构刚度低的薄壁件、曲面件等难加工结构件在传统加工过程中极易出现零件变形较大,加工稳定性不高,颤振严重等现象,造成工件表面质量急剧下降。上述加工缺陷使得所生产零部件的精度和疲劳抗性降低,废品率升高,并大大增加了生产成本,严重限制了这些材料的发展与应用。因此,对制造技术进行革新,选择合适的加工方法以提高难加工材料的切削加工性具有重要意义。
此前,有学者采用非常规加工方法,如电解加
同时,铣削加工因能保证较高的精度要求和加工效率,且适应性较广,已被广泛应用于航空航天制造业、汽车制造等高端领
纵扭复合超声振动系统是LTUVAM加工技术的核心,其功能结构的设计将直接影响超声加工质量与加工成本,主要由超声电源、超声电能传输装置、超声换能器及变幅杆、加工刀具组成。

图1 纵扭超声振动系统示意
Fig.1 Schematic diagram of longitudinal torsional ultrasonic vibration syste
超声电源将电信号转换为与超声振子相匹配的高频交流电信号,从而为LTUVAM提供能量,主要由超声信号产生模块、功率放大模块、频率跟踪模块及外围电路组成。振幅控制和频率自动跟踪是超声电源的关键。随着载荷和刀具磨损量的变化以及超声系统热量的积累,系统的谐振频率发生漂移,进而导致超声振动幅值大大降低,加工稳定性变差。因此,Y.KUAN
超声电能传输装置可跟随铣床主轴高速旋转,并将超声电源产生的高频交流电信号传递给超声换能器。传统超声加工通常采用导电滑环方式,但由于在LTUVAM中主轴高速旋转,导电滑环磨损剧烈,目前已逐渐被非接触能量传输方式所取代。然而,非接触式能量传输系统传输效率较低。为此,X.M.ZH
超声换能器及变幅杆是纵扭复合超声振动系统中的关键部分,换能器可以将高频电能转化为机械振动。变幅杆主要有两个作用:一是放大机械振动质点的位移或速度,使超声波能量集中在一个小的区域,因此它也被称为超声波发射极或超声波集中器;二是用作机械阻抗转换器,即对换能器和声负载之间的阻抗进行匹配,使超声波能量更有效地从换能器传输到负
唐

(a) 纵振模态

(b) 扭振模态
图2 贴片式纵扭复合超声换能器振动模
Fig.2 Vibration mode of patch-type longitudinal torsion composite ultrasonic transduce
M.R.KARAFI

图3 磁致伸缩换能器装配
Fig.3 Magnetic expansion transducer assembly diagra
夹心式压电换能器最早于1917年由法国人保罗·朗之万提

图4 用压电换能器产生纵扭复合超声振动的不同方
Fig.4 Different methods of generating longitudinal torsional composite ultrasonic vibration with piezoelectric transduce

图5 新型柱孔式纵扭转换复合变幅杆的结
Fig.5 Structural diagram of a new cylindrical holes longitudinal torsional conversion composite hor
综上可知,目前针对纵扭复合超声振动系统,研究者主要对其中个别部件独立研究,涉及振动系统中各部件的相关理论缺乏系统性,且振动系统相关参数之间的耦合机制仍不清楚,缺乏整体性研究。同时,应用最广泛的模态退化式压电换能器及变幅杆研究均是通过有限元分析或试验方法进行,以探究斜槽或螺旋槽的结构参数对纵扭共振的影响,并未提出根本原理。
由于在刀具上施加了高频微幅振动,与常规铣削(Conventional milling,CM)相比,LTUVAM具有不同的运动方式,从而导致了不同的切削特性,直接影响材料的切削加工性能。因此,研究LTUVAM的切削特性,对于其在工业中的应用有着重大意义。
J.L.TONG
(1) |
式中,为进给速度,r为铣刀半径,n为主轴速度,f为超声振动频率,A为超声纵向振动振幅,B为超声扭转振动振幅,为超声纵向振动初始相位,为超声扭转振动初始相位。该轨迹方程充分考虑了不同超声振动方向的初始相位,以扭转振幅与半径之比来表示超声扭转振动所引起的旋转角变化,能够准确反映切削刃的运动轨迹,被许多研究者采

图6 LTUVAM切削刃模
Fig.6 LTUVAM cutting blade mode

图7 CM和LTUVAM切削刃轨
Fig.7 CM and LTUVAM cutting blade track
根据
(2) |
对
(3) |
(4) |
LTUVAM具有4点运动特性:周期性接触分离特性、冲击特性、变速特性以及熨压特性。
周期性接触分离特性是指刀-屑、刀-工之间产生周期性的分离,有利于降低切削区域温度,保证刀具锋利性,促进切屑排出,抑制积屑瘤形成。未切削时间(即分离时间)是降低切削力与切削热的重要影响因素,受超声波频率f、超声波振幅A和B、刀具螺旋角β和主轴转速n的影响,当主轴转速超过临界转速时,刀具与工件将不再发生分离过
LTUVAM中,切削刃将具有加速度av,使得刀具具有冲击特性。童志强
综上可知,刀具振动速度及加速度的大小和方向时刻改变,具有变速特性,从而使得刀具实际工作角发生改变,提高实际切削速度,在主轴转速较低的情况下仍能获得高速切削效果。卫
从LTUVAM的运动轨迹可知,刀具在周期性往复运动的同时将对已加工表面进行往复熨压。张存
然而,针对LTUVAM切削特性,学者们只考虑了刀具铣削运动及超声振动的共同作用,而忽略了机床振动与刀具跳动等外界因素对运动轨迹及性能的影响,仍需要进一步修正。并且,目前缺少在实际LTUVAM加工中观测到的刀具运动特性,多数研究是通过理论及仿真进行理想刀具运动轨迹模型的建立,关于超声振动在实际铣削中的微观作用机制仍需深入观测与验证。
LTUVAM已被应用于各类合金材料及复合材料等难加工材料的铣削加工,并表现出了独特的加工优势,包括提高表面质量、提高残余压应力、降低亚表层损伤、减少刀具磨损等。
钛合金由于弹性模量低、切削温度高,易在加工表面产生残余拉应力,是一种典型的难加工材料。G.F.GAO

(a) Al=0 μm, At=0 μm

(b) Al=1 μm, At=0.67 μm

(c) Al=3 μm, At=2 μm

(d) Al=4 μm, At=2.67 μm
图8 不同振幅下Ti-6Al-4V的表面形
Fig.8 Surface topography of Ti-6Al-4V at different amplitude
钛合金薄壁件由于其壁厚较薄、结构刚度低,在铣削过程中变形严重,加工质量差。J.L.TONG
铝合金黏度高且在切削过程中塑性变形严重,加工表面质量差。H.T.WANG

(a) A=0 μm

(b) A=2 μm

(c) A=4 μm

(d) A= 6 μm
图9 不同振幅下的水接触
Fig.9 Water contact angles at different amplitude
SiCp/Al复合材料具有高脆性和低韧性,采用传统加工方法时加工效率低,表面质量差。P.C.PENG

图10 高体分SiCp/Al材料亚表面损
Fig.10 Subsurface damage of high body SiCp / Al materia
采用常规方法加工碳/碳化硅时加工效率偏低,表面质量较差,已无法满足现代制造业的加工要求。唐
J.XU
综上所述,LTUVAM能有效提高材料表面质量,但这种优越性并不是在所有条件下都能体现,超声振幅过大,会使得刀具切削刃与后刀面过度冲击材料表面,恶化材料表面质量。且LTUVAM可以有效降低材料的残余拉应力,提高残余压应力,并降低材料的亚表层损伤。然而,关于LTUVAM碳/碳化硅、芳纶纤维增强材料等复合材料的研究并未引起重视,目前尚未开展广泛研究,LTUVAM对这些复合材料表面及亚表面质量的影响规律尚不明确,有待学者们继续深入研究。
钛合金具有高摩擦因数及高切削热,切削过程易造成严重的刀具磨损。P.M.RINC

图11 不同铣削面积时CM与LTUVAM刀具磨损对
Fig.11 Comparison of CM and LTUVAM tool wear at different milling area
碳/碳化硅材料的高脆性和高硬度是造成铣削过程中刀具磨损的主要原因。唐
碳纤维复合材料(CFRP)具有各向异性,硬度大且导热性差,铣削过程中刀具磨损严重。童志
因此,LTUVAM能有效减少刀具磨损。然而,文献[
现有研究表明,采用LTUVAM铣削难加工材料具有明显优势,可显著提高零件加工质量和刀具使用寿命,是高质高效加工难加工材料的有效方法。但是目前仍存在许多问题需要进一步深入研究,主要包括以下几个方面。
(1)在高速与超高速铣削中采用LTUVAM工艺的刀具-工件接触分离特性不再显著。开发具有更高振动频率、更高机电转化效率(如开发新型材料的压电陶瓷)和更高扭纵比(如设计变幅杆新结构)的超声纵扭振动系统是解决这一问题的有效途径,可以进一步提高LTUVAM的切削工艺性能。
(2)LTUVAM运动轨迹对其切削效果具有决定性影响,但目前在LTUVAM轨迹分析时忽略了机床振动与刀具跳动,使得未切削时间的计算产生一定偏差。建立更加准确的LTUVAM运动轨迹模型,并能适时调整LTUVAM的运动轨迹,对有效提升LTUVAM加工工艺的高质高效切削性能具有重要意义。
(3)将LTUVAM应用于更多难加工材料的切削加工,并对这些材料进行系统性研究,对促进LTUVAM的广泛应用具有重要意义。同时,针对复杂曲面零件和薄壁件的铣削加工,可以将LTUVAM技术与五轴机床相结合,进一步提升复杂曲面零件和薄壁件的加工质量与加工效率。
参考文献
SARKAR B R, DOLOI B, BHATTACHARYYA B. Electrochemical discharge micro-machining of engineering materials[M].Non-traditional Micromachining Processes. Springer, Cham,2017: 367-392. [百度学术]
MANJAIAH M,NARENDRANATH S, BASAVARAJAPPA S. Review on non-conventional machining of shape memory alloys[J]. Transactions of Nonferrous Metals Society of China, 2014, 24(1): 12-21. [百度学术]
AGARWAL N,SHUKLA S,AGARWAL V.Investigation of material removal method in EDM for non-conductive materials[J]. Eur J Adv Eng Technol, 2015, 2(4): 11-13. [百度学术]
GUENOLE J, PRAKASH A, BITZEK E. Atomistic simulations of focused ion beam machining of strained silicon[J]. Applied Surface Science, 2017, 416: 86-95. [百度学术]
PARANDOUSH P, HOSSAIN A. A review of modeling and simulation of laser beam machining[J]. International Journal of Machine Tools and Manufacture,2014,85:135-145. [百度学术]
THOE T B,ASPINWALL D K,Wise M L H.Review on ultrasonic machining[J]. International Journal of Machine Tools and Manufacture, 1998, 38(4): 239-255. [百度学术]
闫晓东. 纵扭复合型超声换能器的设计研究[D]. 北方工业大学, 2015. [百度学术]
YAN X D, The design and research of the longitudinal-torsional composite ultrasonic transducer[D]. North China University of Technology, 2015. [百度学术]
苏永生.铣削Cr12的动态铣削力试验研究[D].天津理工大学, 2011. [百度学术]
SU Y S.Experimental study on milling force of milling Cr12[D]. Tianjin University of Technology, 2011. [百度学术]
GAO G F,XIA Z W,SU T T,et al. Cutting force model of longitudinal-torsional ultrasonic-assisted milling Ti-6Al-4V based on tool flank wear[J].Journal of Materials Processing Technology,2021,291:117042. [百度学术]
KUANG Y,JIN Y,COCHRAN S,et al. Resonance tracking and vibration stablilization for high power ultrasonic transducers[J].Ultrasonics,2014,54(1):187-194. [百度学术]
王佳奇. 纵扭共振超声波发生器设计及辅助铣削工艺过程仿真研究[D].哈尔滨工业大学,2020. [百度学术]
WANG J Q. Longitudinal-torsional resonance ultrasonic generator design and simulation research on auxiliary milling process[D].Harbin Institute of Technology,2020. [百度学术]
ZHU X M,LIN B,LIU L P,et al.Power transfer performance and cutting force effects of contactless energy transfer system for rotary ultrasonic grinding[J].IEEE Transactions on Industrial Electronics,2016,63(5):2785-2795. [百度学术]
许磊. 超声辅助加工共振式无线电能传输系统的研究与开发[D]. 湖南科技大学, 2017. [百度学术]
XU L.Research and development of ultrasonic assisted machining wireless power transmission system based on magnetically-coupled resonant[D].Hunan University of Science and Technology,2017. [百度学术]
LIU J,ZHANG D Y,QIN L G,et al.Feasibility study of the rotary ultrasonic elliptical machining of carbon fiber reinforced plastics (CFRP)[J].International Journal of Machine Tools and Manufacture,2012, 53(1):141-150. [百度学术]
唐军.碳/碳化硅材料纵扭复合超声铣削系统及加工稳定性的研究[D].河南理工大学, 2015. [百度学术]
TANG J.Study on the longitudinal-torsional composite ultrasonic milling system of carbon/silicon carbide and machining stability[D].Henan Polytechnic University, 2015. [百度学术]
KARAFI M R,GHODSI M,HOJJAT Y. Development of magnetostrictive resonant torsional vibrator[J].IEEE Transactions on Magnetics,2015,51(9): 1-8. [百度学术]
贾宝贤,边文凤,赵万生,等.压电超声换能器的应用与发展[J].压电与声光, 2005(02):131-135. [百度学术]
JIA B X, BIAN W F, ZHAO W S,et al.Application and development of piezoelectric ultrasonic transducers[J]. Piezoelectrics & Acoustooptics, 2005(02):131-135. [百度学术]
吴陈军.纵扭共振超声铣削系统研制及其加工实验研究[D].哈尔滨工业大学, 2018. [百度学术]
WU C J.Design and experimental study of longitudinal-torsional vibration assisted milling system[D].Harbin Institute of Technology, 2018. [百度学术]
RINCK P M, SITZBERGER S, ZAEH M F. Actuator design for vibration assisted machining of high performance materials with ultrasonically modulated cutting speed[C]. Fourth European Seminar on Precision Optics Manufacturing. SPIE, 2017, 10326: 68-75. [百度学术]
LIN S Y,GUO H, XX J.Actively adjustable step-type ultrasonic horns in longitudinal vibration[J].Journal of Sound and Vibration, 2018, 419: 367-379. [百度学术]
ASAMI T,MIURA H.Design and experimental investigation of stepped horn with a hollow part to allow individual design of amplitude amplification factors for longitudinal-torsional vibration source[J].Japanese Journal of Applied Physics, 2022. [百度学术]
CHEN T,LIU S L,LIU W,et al.Study on a longitudinal-torsional ultrasonic vibration system with diagonal slits[J]. Advances in Mechanical Engineering,2017,9(7):1305-1310. [百度学术]
LI H B, CHEN T, SONG H, et al. Design and experimental study of longitudinal-torsional ultrasonic transducer with helical slots considering the stiffness variation[J].The International Journal of Advanced Manufacturing Technology,2021,114(9): 3093-3107. [百度学术]
林基艳, 林书玉.新型柱孔式模式转换型纵-扭复合模态超声振动系统[J]. 应用声学, [2023-01-13]:1-8. http://kns.cnki.net/kcms/detail/11.2121.O4.20220829.1848.004.html. [百度学术]
LIN J Y, LIN S Y. Design of a new cylindrical holes mode conversion longitudinal torsional composite mode ultrasonic vibration system[J]. Journal of Applied Acoustics: 1-8[2023-01-13]. http://kns.cnki.net/kcms/detail/11.2121.O4.20220829.1848.004.html. [百度学术]
TONG J L,ZAI P H,CHEN P,et al. Stiffness enhancement analysis of ultrasonic-assisted milling titanium alloy curved thin-walled parts[J]. The International Journal of Advanced Manufacturing Technology,2021,117(1):267-277. [百度学术]
姚成霖.超声波辅助铣削钛合金曲面加工特性研究[D].河南理工大学, 2018. [百度学术]
YAO C L. Research on characteristic of ultrasonic assisted milling on titanium alloy sculptured surfaces[D].Henan Polytechnic University,2018. [百度学术]
许东辉.变螺旋铣刀超声纵扭复合振动铣削铝合金Al7050-T7451表面质量研究[D].河南理工大学,2020. [百度学术]
XU D H.Study on surface quality of Al7050-T7451 milled by ultrasonic longitudinal torsional coupled vibration with variable helix milling cutter[D].Henan Polytechnic University, 2020. [百度学术]
QIN S Q,ZHU L D,WIERCIGROCH M,et al. Material removal and surface generation in longitudinal-torsional ultrasonic assisted milling[J].International Journal of Mechanical Sciences,2022,227:107375. [百度学术]
SHI Z L, XIANG D H, FENG H R, et al. Finite element and experimental analysis of ultrasonic vibration milling of high-volume fraction SiCp/Al composites[J]. International Journal of Precision Engineering and Manufacturing, 2021, 22(10): 1777-1789. [百度学术]
XIANG D H, LI B, PENG P C, et al. Study on formation mechanism of edge defects of high-volume fraction SiCp/Al composites by longitudinal-torsional ultrasonic vibration-assisted milling[J]. Proceedings of the Institution of Mechanical Engineers,Part C:Journal of Mechanical Engineering Science, 2022,236(11):6219-6231. [百度学术]
WU C J, CHEN S J,XIAO C W,et al. Longitudinal-torsional ultrasonic vibration-assisted side milling process[J].Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science,2019,233(10): 3356-3363. [百度学术]
童志强,皮钧.纵扭共振旋转超声端铣碳纤维复合材料的试验研究[J].机械科学与技术,2016,35(03): 425-430. [百度学术]
TONG Z Q, PI J.Experimental study on longitudinal-torsional resonance rotary ultrasonic face milling of CFRP[J]. Mechanical Science and Technology for Aerospace Engineering, 2016,35(03):425-430. [百度学术]
REN W F, XU J K, LIN J Q, et al. Research on homogenization and surface morphology of Ti-6Al-4V alloy by longitudinal-torsional coupled ultrasonic vibration ball-end milling[J].The International Journal of Advanced Manufacturing Technology, 2019, 104(1): 301-313. [百度学术]
卫官. 超声振动铣削钛合金曲面薄壁件切削力特性研究[D]. 河南理工大学, 2019. [百度学术]
WEI G. Research on cutting force characteristics in ultrasonic vibration milling of titanium alloy curved thin-walled parts[D]. Henan Polytechnic University, 2019. [百度学术]
张存鹰,赵波,王晓博.纵扭复合超声端面铣削表面微结构建模与试验研究[J].表面技术,2019,48(10): 52-63,79. [百度学术]
ZHANG C Y, ZHAO B, WANG X B. Modeling and experiment of surface microstructure by longitudinal-torsional compound ultrasonic end milling[J]. Surface Technology, 2019, 48(10): 52-63,79. [百度学术]
PANG Y, FENG P F, WANG J J, et al. Performance analysis of the longitudinal-torsional ultrasonic milling of Ti-6Al-4V[J].The International Journal of Advanced Manufacturing Technology, 2021, 113(5): 1255-1266. [百度学术]
NIU Y, JIAO F, ZHAO B. A novel 3D finite element simulation method for longitudinal-torsional ultrasonic-assisted milling[J].The International Journal of Advanced Manufacturing Technology, 2020, 106(1): 385-400. [百度学术]
NIU Y,JIAO F,ZHAO B,et al.Theoretical investigation of machining-induced residual stresses in longitudinal torsional ultrasonic-assisted milling[J].The International Journal of Advanced Manufacturing Technology, 2020, 108(11): 3689-3705. [百度学术]
XIE W B, WANG X K, ZHAO B, et al. Surface and subsurface analysis of TC18 titanium alloy subject to longitudinal-torsional ultrasonic vibration-assisted end milling[J]. Journal of Alloys and Compounds, 2022,929: 167259. [百度学术]
TONG J L,WEI G,ZHAO L,et al.Surface microstructure of titanium alloy thin-walled parts at ultrasonic vibration-assisted milling[J].The International Journal of Advanced Manufacturing Technology,2019,101(1):1007-1021. [百度学术]
TONG J L,ZHANG Z P,CHEN P,et al.Study on surface morphology of titanium alloy curved thin-walled parts by longitudinal-torsional composite ultrasonic assisted milling[J]. Journal of Manufacturing Processes, 2022, 84: 316-326. [百度学术]
ZHANG Z M,TONG J L,ZHAO J S,et al. Experimental study on surface residual stress of titanium alloy curved thin-walled parts by ultrasonic longitudinal-torsional composite milling[J].The International Journal of Advanced Manufacturing Technology, 2021,115(4):1021-1035. [百度学术]
WANG H T,ZHANG S L,LI G X.Experimental study on ultrasonic-assisted end milling forces in 2195 aluminum-lithium alloy[J]. Materials, 2022, 15(7): 2508. [百度学术]
ZHAO C Y,WANG X B,ZHAO B,et al.Microstructure of high-performance aluminum alloy surface processed by the single-excitation same-frequency longitudinal-torsional coupled ultrasonic vibration milling[J].Materials,2018,11(10): 1975. [百度学术]
PENG P C, XIANG D H, LEI X F, et al. Study on the edge defects of high volume fraction 70% SiCp/Al composites in ultrasonic-assisted milling[J]. The International Journal of Advanced Manufacturing Technology, 2022: 1-14. [百度学术]
LI Y Q,XIANG D H,FENG H R, et al.Surface characteristics investigation of ultrasonic longitudinal-torsional milling of high-volume fraction SiCp/Al[J].The International Journal of Advanced Manufacturing Technology,2020,110(7): 2119-2130. [百度学术]
岳广喜. 超声纵—扭振动高速铣削高体分SiCp/Al复合材料的试验研究[D]. 河南理工大学, 2012. [百度学术]
YUE G X. Experimental research on high volume fraction SiCp/Al composite with ultrasonic longitudinal-torsional vibration high-speed milling[D]. Henan Polytechnic University, 2012. [百度学术]
CHEN J, MING W W, AN Q L, et al. Mechanism and feasibility of ultrasonic-assisted milling to improve the machined surface quality of 2D Cf/SiC composites[J]. Ceramics International, 2020, 46(10): 15122-15136. [百度学术]
XU J, FENG P F, FENG F, et al. Subsurface damage and burr improvements of aramid fiber reinforced plastics by using longitudinal-torsional ultrasonic vibration milling[J]. Journal of Materials Processing Technology,2021,297:117265. [百度学术]
RINCK P M, GUERAY A, KLEINWORT R, et al. Experimental investigations on longitudinal-torsional vibration-assisted milling of Ti-6Al-4V[J].The International Journal of Advanced Manufacturing Technology,2020,108(11):3607-3618. [百度学术]
CHEN P, TONG J L, ZHAO J S, et al. A study ofthe surface microstructure and tool wear of titanium alloys after ultrasonic longitudinal-torsional milling[J].Journal of Manufacturing Processes, 2020,53:1-11. [百度学术]